In short:
1. Thermal - most reliable and precise. Most popular brand - Screen PlateRite (also Heidel Topsetter , agfa Avalon, Fuji T6300 etc) Equipment cost B2 used (full setup) from approx 30-40K EUR. Plate cost approx 5-6EUR/m2.
2. Violet - less reliable (extra plate calibration, required preheat etc), plate cost +2EURm2, equipment cost from 20K EUR. almost everybody (except Kodak) makes this -
3. Conventional - really small installed equipment base because not easy to make equipment (head requires high energy and not so precise light sources). Brands - BasysPrint, Luescher. Basys - low prices, but dont expect high quality from there. Luescher - better quality equipment, higher cost (relatively new equipment), but still with problems.
4. There is another interesting way - CTP based on inkjet and conventional plates (123ctp.com). Quality better than Epson, VMI, Glunz or Coloragte + you can use some conventional plates -> plate price is 4-6 EUR/m2. Price - below 15K EUR new RIP and equipment.
If you ask me - try to find money for thermal and wait for good offer (usually once in 2 months you can find good one). Find good serviceman to teach you for first line service, otherwise you will pay lot of money for 10-30min jobs. I can help you in choosing right configuration.
2 - choose only if you have good plate supplier (with good service and responsibility) and if they know also CTP and related problems. Otherwise you are in trouble. It is possible to work with violet, but you have to get good and smart operator which can troubleshoot problems in their starting phase.
3. - dont know much about them, but look at initial price of conventional CTP and used cost - difference is really big + cost of head exchange is really high.
4 is good, but still not much devices installed, wait for representative in your contry
my 2c